diff --git a/docs/source/doc/kaleidoscope/PythonLangImpl1.rst b/docs/source/doc/kaleidoscope/PythonLangImpl1.rst index 2c5cb45..7b1c3a6 100644 --- a/docs/source/doc/kaleidoscope/PythonLangImpl1.rst +++ b/docs/source/doc/kaleidoscope/PythonLangImpl1.rst @@ -115,7 +115,7 @@ following simple example computes `Fibonacci numbers `_: -.. code-block:: +.. code-block:: python # Compute the x'th fibonacci number. def fib(x): @@ -135,7 +135,7 @@ LLVM JIT makes this completely trivial). This means that you can use the useful for mutually recursive functions). For example: -.. code-block:: +.. code-block:: python extern sin(arg); extern cos(arg); diff --git a/docs/source/doc/kaleidoscope/PythonLangImpl7.rst b/docs/source/doc/kaleidoscope/PythonLangImpl7.rst index 80eb46b..d3dfb74 100644 --- a/docs/source/doc/kaleidoscope/PythonLangImpl7.rst +++ b/docs/source/doc/kaleidoscope/PythonLangImpl7.rst @@ -38,10 +38,17 @@ To understand why mutable variables cause complexities in SSA construction, consider this extremely simple C example: -.. code-block:: python +.. code-block:: c - int G, H; int test(_Bool Condition) { int X; if - (Condition) X = G; else X = H; return X; } + int G, H; + int test(_Bool Condition) { + int X; + if (Condition) + X = G; + else + X = H; + return X; + } @@ -53,12 +60,25 @@ two values. The LLVM IR that we want for this example looks like this: .. code-block:: llvm - @G = weak global i32 0 ; type of @G is i32* @H = - weak global i32 0 ; type of @H is i32* define i32 @test(i1 %Condition) - { entry: br i1 %Condition, label %cond_true, label %cond_false - cond_true: %X.0 = load i32* @G br label %cond_next cond_false: %X.1 - = load i32* @H br label %cond_next cond_next: %X.2 = phi i32 [ %X.1, - %cond_false ], [ %X.0, %cond_true ] ret i32 %X.2 } + @G = weak global i32 0 ; type of @G is i32* + @H = weak global i32 0 ; type of @H is i32* + + define i32 @test(i1 %Condition) { + entry: + + br i1 %Condition, label %cond_true, label %cond_false + + cond_true: + %X.0 = load i32* @G + br label %cond_next + + cond_false: + %X.1 = load i32* @H + br label %cond_next + + cond_next: + %X.2 = phi i32 [ %X.1, %cond_false ], [ %X.0, %cond_true ] + ret i32 %X.2 } @@ -109,12 +129,16 @@ variable definitions, they are declared with the `LLVM alloca instruction `_: -.. code-block:: python +.. code-block:: llvm - define i32 @example() { entry: %X = alloca i32 ; - type of %X is i32\ *. ... %tmp = load i32* %X ; load the stack value %X - from the stack. %tmp2 = add i32 %tmp, 1 ; increment it store i32 %tmp2, - i32* %X ; store it back ... + define i32 @example() { + entry: + %X = alloca i32 ; type of %X is i32 *. + ... + %tmp = load i32* %X ; load the stack value %X from the stack. + %tmp2 = add i32 %tmp, 1 ; increment it store i32 %tmp2, + i32* %X ; store it back + ... @@ -128,73 +152,69 @@ using a PHI node: .. code-block:: llvm - @G = weak global i32 0 ; type of @G is i32* @H = - weak global i32 0 ; type of @H is i32* define i32 @test(i1 %Condition) - { entry: %X = alloca i32 ; type of %X is i32\ *. br i1 %Condition, label - %cond_true, label %cond_false cond_true: %X.0 = load i32* @G store - i32 %X.0, i32* %X ; Update X br label %cond_next cond_false: %X.1 = - load i32* @H store i32 %X.1, i32* %X ; Update X br label %cond_next - cond_next: %X.2 = load i32* %X ; Read X ret i32 %X.2 } {% endhighlight - %} + @G = weak global i32 0 ; type of @G is i32* + @H = weak global i32 0 ; type of @H is i32* + + define i32 @test(i1 %Condition) { + entry: + %X = alloca i32 ; type of %X is i32 *. + br i1 %Condition, label %cond_true, label %cond_false + + cond_true: + %X.0 = load i32* @G + store i32 %X.0, i32* %X ; Update X + br label %cond_next + + cond_false: + %X.1 = load i32* @H + store i32 %X.1, i32* %X ; Update X + br label %cond_next - With this, we have discovered a way to handle arbitrary mutable - variables without the need to create Phi nodes at all: + cond_next: + %X.2 = load i32* %X ; Read X + ret i32 %X.2 + } - .. raw:: html - -
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  1. - - Each mutable variable becomes a stack allocation. - - .. raw:: html - -
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  2. - - Each read of the variable becomes a load from the stack. - - .. raw:: html - -
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  3. - - Each update of the variable becomes a store to the stack. - - .. raw:: html - -
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  4. - - Taking the address of a variable just uses the stack address directly. - - .. raw:: html - -
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- - While this solution has solved our immediate problem, it introduced - another one: we have now apparently introduced a lot of stack traffic - for very simple and common operations, a major performance problem. - Fortunately for us, the LLVM optimizer has a highly-tuned optimization - pass named "mem2reg" that handles this case, promoting allocas like this - into SSA registers, inserting Phi nodes as appropriate. If you run this - example through the pass, for example, you'll get: +With this, we have discovered a way to handle arbitrary mutable +variables without the need to create Phi nodes at all: + +#. Each mutable variable becomes a stack allocation. +#. Each read of the variable becomes a load from the stack. +#. Each update of the variable becomes a store to the stack. +#. Taking the address of a variable just uses the stack address directly. + +While this solution has solved our immediate problem, it introduced +another one: we have now apparently introduced a lot of stack traffic +for very simple and common operations, a major performance problem. +Fortunately for us, the LLVM optimizer has a highly-tuned optimization +pass named "mem2reg" that handles this case, promoting allocas like this +into SSA registers, inserting Phi nodes as appropriate. If you run this +example through the pass, for example, you'll get: + +.. code-block:: bash $ llvm-as < example.ll | opt -mem2reg | llvm-dis - - - - - .. code-block:: llvm - @G = weak global i32 0 @H = weak global i32 0 - define i32 @test(i1 %Condition) { entry: br i1 %Condition, label - %cond_true, label %cond_false cond_true: %X.0 = load i32* @G br - label %cond_next cond_false: %X.1 = load i32* @H br label %cond_next - cond_next: %X.01 = phi i32 [ %X.1, %cond_false ], [ %X.0, %cond_true - ] ret i32 %X.01 } + @G = weak global i32 0 + @H = weak global i32 0 + + define i32 @test(i1 %Condition) { + entry: + br i1 %Condition, label %cond_true, label %cond_false + + cond_true: + %X.0 = load i32* @G + br label %cond_next + + cond_false: + %X.1 = load i32* @H + br label %cond_next + + cond_next: + %X.01 = phi i32 [ %X.1, %cond_false ], [ %X.0, %cond_true ] + ret i32 %X.01 + } @@ -205,21 +225,21 @@ pass is the answer to dealing with mutable variables, and we highly recommend that you depend on it. Note that mem2reg only works on variables in certain circumstances: -- mem2reg is alloca-driven: it looks for allocas and if it can handle +#. mem2reg is alloca-driven: it looks for allocas and if it can handle them, it promotes them. It does not apply to global variables or heap allocations. -- mem2reg only looks for alloca instructions in the entry block of the +#. mem2reg only looks for alloca instructions in the entry block of the function. Being in the entry block guarantees that the alloca is only executed once, which makes analysis simpler. -- mem2reg only promotes allocas whose uses are direct loads and stores. +#. mem2reg only promotes allocas whose uses are direct loads and stores. If the address of the stack object is passed to a function, or if any funny pointer arithmetic is involved, the alloca will not be promoted. -- mem2reg only works on allocas of `first - class `_ +#. mem2reg only works on allocas of `first class + `_ values (such as pointers, scalars and vectors), and only if the array size of the allocation is 1 (or missing in the .ll file). mem2reg is not capable of promoting structs or arrays to registers. Note that @@ -265,8 +285,8 @@ Now that we know the sort of problem we want to tackle, lets see what this looks like in the context of our little Kaleidoscope language. We're going to add two features: -- The ability to mutate variables with the '=' operator. -- The ability to define new variables. +#. The ability to mutate variables with the '=' operator. +#. The ability to define new variables. While the first item is really what this is about, we only have variables for incoming arguments as well as for induction variables, and @@ -275,18 +295,27 @@ variables is a useful thing regardless of whether you will be mutating them. Here's a motivating example that shows how we could use these: -.. code-block:: python +.. code-block:: - # Define ':' for sequencing: as a low-precedence - operator that ignores operands # and just returns the RHS. def binary : - 1 (x y) y; + # Define ':' for sequencing: as a low-precedence operator that ignores operands + # and just returns the RHS. + def binary : 1 (x y) y; # Recursive fib, we could do this before. - def fib(x) if (x < 3) then 1 else fib(x-1) + fib(x-2) + def fib(x) + if (x < 3) then + 1 + else + fib(x-1) + fib(x-2) # Iterative fib. - def fibi(x) var a = 1, b = 1, c in (for i = 3, i < x in c = a + b : a = - b : b = c) : b + def fibi(x) + var a = 1, b = 1, c in + (for i = 3, i < x in + c = a + b : + a = b : + b = c) : + b # Call it. fibi(10) @@ -323,14 +352,15 @@ function that ensures that the allocas are created in the entry block of the function: -.. code-block:: python +.. code-block:: - # Creates an alloca instruction in the entry - block of the function. This is used # for mutable variables. def - CreateEntryBlockAlloca(function, var_name): entry = - function.get_entry_basic_block() builder = Builder.new(entry) - builder.position_at_beginning(entry) return - builder.alloca(Type.double(), var_name) + # Creates an alloca instruction in the entry block of the function. This is used + # for mutable variables. + def CreateEntryBlockAlloca(function, var_name): + entry = function.get_entry_basic_block() + builder = Builder.new(entry) + builder.position_at_beginning(entry) return + builder.alloca(Type.double(), var_name) @@ -347,43 +377,44 @@ from the stack slot: .. code-block:: python - def CodeGen(self): if self.name in - g_named_values: return - g_llvm_builder.load(g_named_values[self.name], self.name) else: - raise RuntimeError('Unknown variable name: ' + self.name) + def CodeGen(self): + if self.name in g_named_values: + return g_llvm_builder.load(g_named_values[self.name], self.name) + else: + raise RuntimeError('Unknown variable name: ' + self.name) - As you can see, this is pretty straightforward. Now we need to update - the things that define the variables to set up the alloca. We'll start - with ``ForExpressionNode.CodeGen`` (see the `full code listing <#code>`_ - for the unabridged code): +As you can see, this is pretty straightforward. Now we need to update +the things that define the variables to set up the alloca. We'll start +with ``ForExpressionNode.CodeGen`` (see the :ref:`full code listing ` +for the unabridged code): + +.. code-block:: python - def CodeGen(self): function = - g_llvm_builder.basic_block.function - - :: - - # Create an alloca for the variable in the entry block. - alloca = CreateEntryBlockAlloca(function, self.loop_variable) - - # Emit the start code first, without 'variable' in scope. - start_value = self.start.CodeGen() - - # Store the value into the alloca. - g_llvm_builder.store(start_value, alloca) - ... - # Compute the end condition. - end_condition = self.end.CodeGen() - - # Reload, increment, and restore the alloca. This handles the case where - # the body of the loop mutates the variable. - cur_value = g_llvm_builder.load(alloca, self.loop_variable) - next_value = g_llvm_builder.fadd(cur_value, step_value, 'nextvar') - g_llvm_builder.store(next_value, alloca) - - # Convert condition to a bool by comparing equal to 0.0. - end_condition_bool = g_llvm_builder.fcmp( - FCMP_ONE, end_condition, Constant.real(Type.double(), 0), 'loopcond') - ... + def CodeGen(self): + function = g_llvm_builder.basic_block.function + + # Create an alloca for the variable in the entry block. + alloca = CreateEntryBlockAlloca(function, self.loop_variable) + + # Emit the start code first, without 'variable' in scope. + start_value = self.start.CodeGen() + + # Store the value into the alloca. + g_llvm_builder.store(start_value, alloca) + ... + # Compute the end condition. + end_condition = self.end.CodeGen() + + # Reload, increment, and restore the alloca. This handles the case where + # the body of the loop mutates the variable. + cur_value = g_llvm_builder.load(alloca, self.loop_variable) + next_value = g_llvm_builder.fadd(cur_value, step_value, 'nextvar') + g_llvm_builder.store(next_value, alloca) + + # Convert condition to a bool by comparing equal to 0.0. + end_condition_bool = g_llvm_builder.fcmp( + FCMP_ONE, end_condition, Constant.real(Type.double(), 0), 'loopcond') + ... @@ -400,12 +431,15 @@ them. The code for this is also pretty simple: .. code-block:: python - class PrototypeNode(object): ... # Create an - alloca for each argument and register the argument in the symbol # table - so that references to it will succeed. def CreateArgumentAllocas(self, - function): for arg_name, arg in zip(self.args, function.args): alloca = - CreateEntryBlockAlloca(function, arg_name) g_llvm_builder.store(arg, - alloca) g_named_values[arg_name] = alloca + class PrototypeNode(object): + ... + # Create an alloca for each argument and register the argument in the symbol + # table so that references to it will succeed. + def CreateArgumentAllocas(self, function): + for arg_name, arg in zip(self.args, function.args): + alloca = CreateEntryBlockAlloca(function, arg_name) + g_llvm_builder.store(arg, alloca) + g_named_values[arg_name] = alloca @@ -420,54 +454,91 @@ get good codegen once again: .. code-block:: python - from llvm.passes import - (PASS_PROMOTE_MEMORY_TO_REGISTER, PASS_INSTRUCTION_COMBINING, - PASS_REASSOCIATE, PASS_GVN, PASS_CFG_SIMPLIFICATION) ... def main(): - # Set up the optimizer pipeline. Start with registering info about how - the # target lays out data structures. - g_llvm_pass_manager.add(g_llvm_executor.target_data) # Promote - allocas to registers. - g_llvm_pass_manager.add(PASS_PROMOTE_MEMORY_TO_REGISTER) # Do - simple "peephole" optimizations and bit-twiddling optzns. - g_llvm_pass_manager.add(PASS_INSTRUCTION_COMBINING) # Reassociate - expressions. g_llvm_pass_manager.add(PASS_REASSOCIATE) + from llvm.passes import (PASS_PROMOTE_MEMORY_TO_REGISTER, + PASS_INSTRUCTION_COMBINING, + PASS_REASSOCIATE, + PASS_GVN, + PASS_CFG_SIMPLIFICATION) + ... + def main(): + # Set up the optimizer pipeline. Start with registering info about how the + # target lays out data structures. + g_llvm_pass_manager.add(g_llvm_executor.target_data) + # Promote allocas to registers. + g_llvm_pass_manager.add(PASS_PROMOTE_MEMORY_TO_REGISTER) + # Do simple "peephole" optimizations and bit-twiddling optzns. + g_llvm_pass_manager.add(PASS_INSTRUCTION_COMBINING) + # Reassociate expressions. + g_llvm_pass_manager.add(PASS_REASSOCIATE) - It is interesting to see what the code looks like before and after the - mem2reg optimization runs. For example, this is the before/after code - for our recursive fib function. Before the optimization: +It is interesting to see what the code looks like before and after the +mem2reg optimization runs. For example, this is the before/after code +for our recursive fib function. Before the optimization: + +.. code-block:: - define double @fib(double %x) { entry: %x1 = alloca - double store double %x, double* %x1 %x2 = load double* %x1 %cmptmp = - fcmp ult double %x2, 3.000000e+00 %booltmp = uitofp i1 %cmptmp to double - %ifcond = fcmp one double %booltmp, 0.000000e+00 br i1 %ifcond, label - %then, label %else then: ; preds = %entry br label %ifcont else: ; preds - = %entry %x3 = load double* %x1 %subtmp = fsub double %x3, 1.000000e+00 - %calltmp = call double @fib(double %subtmp) %x4 = load double* %x1 - %subtmp5 = fsub double %x4, 2.000000e+00 %calltmp6 = call double - @fib(double %subtmp5) %addtmp = fadd double %calltmp, %calltmp6 br label - %ifcont ifcont: ; preds = %else, %then %iftmp = phi double [ - 1.000000e+00, %then ], [ %addtmp, %else ] ret double %iftmp } + define double @fib(double %x) { + entry: + %x1 = alloca double + store double %x, double* %x1 + %x2 = load double* %x1 + %cmptmp = fcmp ult double %x2, 3.000000e+00 + %booltmp = uitofp i1 %cmptmp to double + %ifcond = fcmp one double %booltmp, 0.000000e+00 + br i1 %ifcond, label %then, label %else + + then: ; preds = %entry + br label %ifcont + + else: ; preds = %entry + %x3 = load double* %x1 + %subtmp = fsub double %x3, 1.000000e+00 + %calltmp = call double @fib(double %subtmp) + %x4 = load double* %x1 + %subtmp5 = fsub double %x4, 2.000000e+00 + %calltmp6 = call double @fib(double %subtmp5) + %addtmp = fadd double %calltmp, %calltmp6 + br label %ifcont + + ifcont: ; preds = %else, %then + %iftmp = phi double [ 1.000000e+00, %then ], [ %addtmp, %else ] + ret double %iftmp } - Here there is only one variable (x, the input argument) but you can - still see the extremely simple-minded code generation strategy we are - using. In the entry block, an alloca is created, and the initial input - value is stored into it. Each reference to the variable does a reload - from the stack. Also, note that we didn't modify the if/then/else - expression, so it still inserts a PHI node. While we could make an - alloca for it, it is actually easier to create a PHI node for it, so we - still just make the PHI. +Here there is only one variable (x, the input argument) but you can +still see the extremely simple-minded code generation strategy we are +using. In the entry block, an alloca is created, and the initial input +value is stored into it. Each reference to the variable does a reload +from the stack. Also, note that we didn't modify the if/then/else +expression, so it still inserts a PHI node. While we could make an +alloca for it, it is actually easier to create a PHI node for it, so we +still just make the PHI. + +Here is the code after the mem2reg pass runs: + +.. code-block:: - Here is the code after the mem2reg pass runs: + define double @fib(double %x) { + entry: + %cmptmp = fcmp ult double %x, 3.000000e+00 + %booltmp = uitofp i1 %cmptmp to double + %ifcond = fcmp one double %booltmp, 0.000000e+00 + br i1 %ifcond, label %then, label %else + + then: + br label %ifcont + + else: + %subtmp = fsub double %x, 1.000000e+00 + %calltmp = call double @fib(double %subtmp) + %subtmp5 = fsub double %x, 2.000000e+00 + %calltmp6 = call double @fib(double %subtmp5) %addtmp = fadd double %calltmp, %calltmp6 + br label %ifcont - define double @fib(double %x) { entry: %cmptmp = - fcmp ult double %x, 3.000000e+00 %booltmp = uitofp i1 %cmptmp to double - %ifcond = fcmp one double %booltmp, 0.000000e+00 br i1 %ifcond, label - %then, label %else then: br label %ifcont else: %subtmp = fsub double - %x, 1.000000e+00 %calltmp = call double @fib(double %subtmp) %subtmp5 = - fsub double %x, 2.000000e+00 %calltmp6 = call double @fib(double - %subtmp5) %addtmp = fadd double %calltmp, %calltmp6 br label %ifcont - ifcont: ; preds = %else, %then %iftmp = phi double [ 1.000000e+00, %then - ], [ %addtmp, %else ] ret double %iftmp } + ifcont: ; preds = %else, %then + %iftmp = phi double [ 1.000000e+00, %then + ], [ %addtmp, %else ] + ret double %iftmp + } @@ -480,14 +551,24 @@ After the rest of the optimizers run, we get: .. code-block:: llvm - define double @fib(double %x) { entry: %cmptmp = - fcmp ult double %x, 3.000000e+00 %booltmp = uitofp i1 %cmptmp to double - %ifcond = fcmp ueq double %booltmp, 0.000000e+00 br i1 %ifcond, label - %else, label %ifcont else: %subtmp = fsub double %x, 1.000000e+00 - %calltmp = call double @fib(double %subtmp) %subtmp5 = fsub double %x, - 2.000000e+00 %calltmp6 = call double @fib(double %subtmp5) %addtmp = - fadd double %calltmp, %calltmp6 ret double %addtmp ifcont: ret double - 1.000000e+00 } + define double @fib(double %x) { + entry: + %cmptmp = fcmp ult double %x, 3.000000e+00 + %booltmp = uitofp i1 %cmptmp to double + %ifcond = fcmp ueq double %booltmp, 0.000000e+00 + br i1 %ifcond, label %else, label %ifcont + + else: + %subtmp = fsub double %x, 1.000000e+00 + %calltmp = call double @fib(double %subtmp) + %subtmp5 = fsub double %x, 2.000000e+00 + %calltmp6 = call double @fib(double %subtmp5) + %addtmp = fadd double %calltmp, %calltmp6 + ret double %addtmp + + ifcont: + ret double 1.000000e+00 + } @@ -511,40 +592,50 @@ step is to set a precedence: .. code-block:: python - def main(): ... # Install standard binary - operators. # 1 is lowest possible precedence. 40 is the highest. - g_binop_precedence['='] = 2 g_binop_precedence['<'] = 10 - g_binop_precedence['+'] = 20 g_binop_precedence['-'] = 20 + def main(): + ... + # Install standard binary operators. + # 1 is lowest possible precedence. 40 is the highest. + g_binop_precedence['='] = 2 + g_binop_precedence['<'] = 10 + g_binop_precedence['+'] = 20 + g_binop_precedence['-'] = 20 - Now that the parser knows the precedence of the binary operator, it - takes care of all the parsing and AST generation. We just need to - implement codegen for the assignment operator. This looks like: +Now that the parser knows the precedence of the binary operator, it +takes care of all the parsing and AST generation. We just need to +implement codegen for the assignment operator. This looks like: + +.. code-block:: python - class - BinaryOperatorExpressionNode(ExpressionNode): ... def CodeGen(self): # A - special case for '=' because we don't want to emit the LHS as an # - expression. if self.operator == '=': # Assignment requires the LHS to be - an identifier. if not isinstance(self.left, VariableExpressionNode): - raise RuntimeError('Destination of "=" must be a variable.') + class BinaryOperatorExpressionNode(ExpressionNode): + ... + def CodeGen(self): + # A special case for '=' because we don't want to emit the LHS as an + # expression. + if self.operator == '=': + # Assignment requires the LHS to be an identifier. + if not isinstance(self.left, VariableExpressionNode): + raise RuntimeError('Destination of "=" must be a variable.') - Unlike the rest of the binary operators, our assignment operator doesn't - follow the "emit LHS, emit RHS, do computation" model. As such, it is - handled as a special case before the other binary operators are handled. - The other strange thing is that it requires the LHS to be a variable. It - is invalid to have ``(x+1) = expr`` -- only things like ``x = expr`` are - allowed. - - # Codegen the RHS. value = self.right.CodeGen() - - :: - - # Look up the name. - variable = g_named_values[self.left.name] - - # Store the value and return it. - g_llvm_builder.store(value, variable) - - return value +Unlike the rest of the binary operators, our assignment operator doesn't +follow the "emit LHS, emit RHS, do computation" model. As such, it is +handled as a special case before the other binary operators are handled. +The other strange thing is that it requires the LHS to be a variable. It +is invalid to have ``(x+1) = expr`` -- only things like ``x = expr`` are +allowed. + +.. code-block:: python + + # Codegen the RHS. + value = self.right.CodeGen() + + # Look up the name. + variable = g_named_values[self.left.name] + + # Store the value and return it. + g_llvm_builder.store(value, variable) + + return value ... @@ -560,15 +651,19 @@ Now that we have an assignment operator, we can mutate loop variables and arguments. For example, we can now run code like this: -.. code-block:: python +.. code-block:: - # Function to print a double. extern printd(x) + # Function to print a double. + extern printd(x) # Define ':' for sequencing: as a low-precedence operator that ignores operands # and just returns the RHS. def binary : 1 (x y) y - def test(x) printd(x) : x = 4 : printd(x) + def test(x) + printd(x) : + x = 4 : + printd(x) test(123) @@ -594,10 +689,20 @@ this: .. code-block:: python - ... class UnaryToken(object): pass class - VarToken(object): pass ... def Tokenize(string): ... elif identifier == - 'unary': yield UnaryToken() elif identifier == 'var': yield VarToken() - else: yield IdentifierToken(identifier) + ... + class UnaryToken(object): + pass + class VarToken(object): + pass + ... + def Tokenize(string): + ... + elif identifier == 'unary': + yield UnaryToken() + elif identifier == 'var': + yield VarToken() + else: + yield IdentifierToken(identifier) @@ -607,13 +712,15 @@ var/in, it looks like this: .. code-block:: python - # Expression class for var/in. class - VarExpressionNode(ExpressionNode): + # Expression class for var/in. + class VarExpressionNode(ExpressionNode): - def __init__(self, variables, body): self.variables = variables - self.body = body - - def CodeGen(self): ... + def __init__(self, variables, body): + self.variables = variables + self.body = body + + def CodeGen(self): + ... @@ -628,16 +735,23 @@ do is add it as a primary expression: .. code-block:: python - # primary ::= # dentifierexpr | numberexpr | - parenexpr | ifexpr | forexpr | varexpr def ParsePrimary(self): if - isinstance(self.current, IdentifierToken): return - self.ParseIdentifierExpr() elif isinstance(self.current, NumberToken): - return self.ParseNumberExpr() elif isinstance(self.current, IfToken): - return self.ParseIfExpr() elif isinstance(self.current, ForToken): - return self.ParseForExpr() elif isinstance(self.current, VarToken): - return self.ParseVarExpr() elif self.current == CharacterToken('('): - return self.ParseParenExpr() else: raise RuntimeError('Unknown token - when expecting an expression.') + # primary ::= + # dentifierexpr | numberexpr | parenexpr | ifexpr | forexpr | varexpr + def ParsePrimary(self): + if isinstance(self.current, IdentifierToken): + return self.ParseIdentifierExpr() + elif isinstance(self.current, NumberToken): + return self.ParseNumberExpr() + elif isinstance(self.current, IfToken): + return self.ParseIfExpr() + elif isinstance(self.current, ForToken): + return self.ParseForExpr() + elif isinstance(self.current, VarToken): + return self.ParseVarExpr() + elif self.current == CharacterToken('('): + return self.ParseParenExpr() + else: + raise RuntimeError('Unknown token when expecting an expression.') @@ -646,67 +760,52 @@ Next we define ParseVarExpr: .. code-block:: python - # varexpr ::= 'var' (identifier ('=' - expression)?)+ 'in' expression def ParseVarExpr(self): self.Next() # eat - 'var'. - - :: - - variables = {} - - # At least one variable name is required. - if not isinstance(self.current, IdentifierToken): - raise RuntimeError('Expected identifier after "var".') - + # varexpr ::= 'var' (identifier ('=' expression)?)+ 'in' expression + def ParseVarExpr(self): + self.Next() # eat 'var'. + + variables = {} + + # At least one variable name is required. + if not isinstance(self.current, IdentifierToken): + raise RuntimeError('Expected identifier after "var".') + #The first part of this code parses the list of identifier/expr pairs + #into the local variables list. + while True: + var_name = self.current.name + self.Next() # eat the identifier. -The first part of this code parses the list of identifier/expr pairs -into the local ``variables`` list. - - -.. code-block:: python - - while True: var_name = self.current.name - self.Next() # eat the identifier. - - :: - - # Read the optional initializer. - if self.current == CharacterToken('='): - self.Next() # eat '='. - variables[var_name] = self.ParseExpression() - else: - variables[var_name] = None - - # End of var list, exit loop. - if self.current != CharacterToken(','): - break - self.Next() # eat ','. - - if not isinstance(self.current, IdentifierToken): - raise RuntimeError('Expected identifier after "," in a var expression.') + # Read the optional initializer. + if self.current == CharacterToken('='): + self.Next() # eat '='. + variables[var_name] = self.ParseExpression() + else: + variables[var_name] = None + + # End of var list, exit loop. + if self.current != CharacterToken(','): + break + self.Next() # eat ','. + + if not isinstance(self.current, IdentifierToken): + raise RuntimeError('Expected identifier after "," in a var expression.') + # Once all the variables are parsed, we then parse the body and create the + # AST node: + # At this point, we have to have 'in'. + if not isinstance(self.current, InToken): + raise RuntimeError('Expected "in" keyword after "var".') + self.Next() # eat 'in'. -Once all the variables are parsed, we then parse the body and create the -AST node: - - -.. code-block:: python - - # At this point, we have to have 'in'. if not - isinstance(self.current, InToken): raise RuntimeError('Expected "in" - keyword after "var".') self.Next() # eat 'in'. - - :: - - body = self.ParseExpression() - - return VarExpressionNode(variables, body) + body = self.ParseExpression() + + return VarExpressionNode(variables, body) @@ -718,35 +817,35 @@ emission of LLVM IR for it. This code starts out with: .. code-block:: python - class VarExpressionNode(ExpressionNode): ... def - CodeGen(self): old_bindings = {} function = - g_llvm_builder.basic_block.function - - :: - - # Register all variables and emit their initializer. - for var_name, var_expression in self.variables.iteritems(): - # Emit the initializer before adding the variable to scope, this prevents - # the initializer from referencing the variable itself, and permits stuff - # like this: - # var a = 1 in - # var a = a in ... # refers to outer 'a'. - if var_expression is not None: - var_value = var_expression.CodeGen() - else: - var_value = Constant.real(Type.double(), 0) - - alloca = CreateEntryBlockAlloca(function, var_name) - g_llvm_builder.store(var_value, alloca) - - # Remember the old variable binding so that we can restore the binding - # when we unrecurse. - old_bindings[var_name] = g_named_values.get(var_name, None) - - # Remember this binding. - g_named_values[var_name] = alloca - - + class VarExpressionNode(ExpressionNode): + ... + def CodeGen(self): + old_bindings = {} + function = g_llvm_builder.basic_block.function + + # Register all variables and emit their initializer. + for var_name, var_expression in self.variables.iteritems(): + # Emit the initializer before adding the variable to scope, this prevents + # the initializer from referencing the variable itself, and permits stuff + # like this: + # var a = 1 in + # var a = a in ... # refers to outer 'a'. + if var_expression is not None: + var_value = var_expression.CodeGen() + else: + var_value = Constant.real(Type.double(), 0) + + alloca = CreateEntryBlockAlloca(function, var_name) + g_llvm_builder.store(var_value, alloca) + + # Remember the old variable binding so that we can restore the binding + # when we unrecurse. + old_bindings[var_name] = g_named_values.get(var_name, None) + + # Remember this binding. + g_named_values[var_name] = alloca + + @@ -762,8 +861,8 @@ we evaluate the body of the var/in expression: .. code-block:: python - # Codegen the body, now that all vars are in - scope. body = self.body.CodeGen() + # Codegen the body, now that all vars are in scope. + body = self.body.CodeGen() @@ -772,13 +871,13 @@ Finally, before returning, we restore the previous variable bindings: .. code-block:: python - # Pop all our variables from scope. for var_name - in self.variables: if old_bindings[var_name] is not None: - g_named_values[var_name] = old_bindings[var_name] else: del - g_named_values[var_name] - - :: - + # Pop all our variables from scope. + for var_name in self.variables: + if old_bindings[var_name] is not None: + g_named_values[var_name] = old_bindings[var_name] + else: + del g_named_values[var_name] + # Return the body computation. return body @@ -797,6 +896,8 @@ dominance frontier" computation anywhere in sight. -------------- +.. _code: + Full Code Listing =========================== @@ -808,17 +909,23 @@ mutable variables and var/in support: #!/usr/bin/env python - import re from llvm.core import Module, Constant, Type, Function, - Builder from llvm.ee import ExecutionEngine, TargetData from llvm.passes - import FunctionPassManager + import re + from llvm.core import Module, Constant, Type, Function, Builder + from llvm.ee import ExecutionEngine, TargetData + from llvm.passes import FunctionPassManager - from llvm.core import FCMP_ULT, FCMP_ONE from llvm.passes import - (PASS_PROMOTE_MEMORY_TO_REGISTER, PASS_INSTRUCTION_COMBINING, - PASS_REASSOCIATE, PASS_GVN, PASS_CFG_SIMPLIFICATION) + from llvm.core import FCMP_ULT, FCMP_ONE + from llvm.passes import(PASS_PROMOTE_MEMORY_TO_REGISTER, + PASS_INSTRUCTION_COMBINING, + PASS_REASSOCIATE, + PASS_GVN, + PASS_CFG_SIMPLIFICATION) - Globals - ------- +Globals +------- +.. code-block:: python + # The LLVM module, which holds all the IR code. g_llvm_module = Module.new('my cool jit') @@ -840,767 +947,889 @@ mutable variables and var/in support: # Creates an alloca instruction in the entry block of the function. This is used # for mutable variables. - def CreateEntryBlockAlloca(function, var_name): entry = - function.get_entry_basic_block() builder = Builder.new(entry) - builder.position_at_beginning(entry) return - builder.alloca(Type.double(), var_name) + def CreateEntryBlockAlloca(function, var_name): + entry = function.get_entry_basic_block() + builder = Builder.new(entry) + builder.position_at_beginning(entry) + return builder.alloca(Type.double(), var_name) - Lexer - ----- +Lexer +----- + +.. code-block:: python # The lexer yields one of these types for each token. - class EOFToken(object): pass class DefToken(object): pass class - ExternToken(object): pass class IfToken(object): pass class - ThenToken(object): pass class ElseToken(object): pass class - ForToken(object): pass class InToken(object): pass class - BinaryToken(object): pass class UnaryToken(object): pass class - VarToken(object): pass + class EOFToken(object): + pass + class DefToken(object): + pass + class ExternToken(object): + pass + class IfToken(object): + pass + class ThenToken(object): + pass + class ElseToken(object): + pass + class ForToken(object): + pass + class InToken(object): + pass + class BinaryToken(object): + pass + class UnaryToken(object): + pass + class VarToken(object): + pass - class IdentifierToken(object): def __init__(self, name): self.name = - name + class IdentifierToken(object): + def __init__(self, name): + self.name = name - class NumberToken(object): def __init__(self, value): self.value = - value + class NumberToken(object): + def __init__(self, value): + self.value = value - class CharacterToken(object): def __init__(self, char): self.char = - char def __eq__(self, other): return isinstance(other, CharacterToken) - and self.char == other.char def __ne__(self, other): return not self - == other + class CharacterToken(object): + def __init__(self, char): + self.char = char + def __eq__(self, other): + return isinstance(other, CharacterToken) and self.char == other.char + def __ne__(self, other): + return not self == other # Regular expressions that tokens and comments of our language. - REGEX_NUMBER = re.compile('[0-9]+(?:.[0-9]+)?') REGEX_IDENTIFIER = - re.compile('[a-zA-Z][a-zA-Z0-9]\ *') REGEX_COMMENT = re.compile('#.*') + REGEX_NUMBER = re.compile('[0-9]+(?:\.[0-9]+)?') + REGEX_IDENTIFIER = re.compile('[a-zA-Z][a-zA-Z0-9] *') + REGEX_COMMENT = re.compile('#.*') - def Tokenize(string): while string: # Skip whitespace. if - string[0].isspace(): string = string[1:] continue + def Tokenize(string): + while string: + # Skip whitespace. + if string[0].isspace(): + string = string[1:] + continue + + # Run regexes. + comment_match = REGEX_COMMENT.match(string) + number_match = REGEX_NUMBER.match(string) + identifier_match = REGEX_IDENTIFIER.match(string) + + # Check if any of the regexes matched and yield the appropriate result. + if comment_match: + comment = comment_match.group(0) + string = string[len(comment):] + elif number_match: + number = number_match.group(0) + yield NumberToken(float(number)) + string = string[len(number):] + elif identifier_match: + identifier = identifier_match.group(0) + # Check if we matched a keyword. + if identifier == 'def': + yield DefToken() + elif identifier == 'extern': + yield ExternToken() + elif identifier == 'if': + yield IfToken() + elif identifier == 'then': + yield ThenToken() + elif identifier == 'else': + yield ElseToken() + elif identifier == 'for': + yield ForToken() + elif identifier == 'in': + yield InToken() + elif identifier == 'binary': + yield BinaryToken() + elif identifier == 'unary': + yield UnaryToken() + elif identifier == 'var': + yield VarToken() + else: + yield IdentifierToken(identifier) + string = string[len(identifier):] + else: + # Yield the ASCII value of the unknown character. + yield CharacterToken(string[0]) + string = string[1:] + + yield EOFToken() - :: - - # Run regexes. - comment_match = REGEX_COMMENT.match(string) - number_match = REGEX_NUMBER.match(string) - identifier_match = REGEX_IDENTIFIER.match(string) - - # Check if any of the regexes matched and yield the appropriate result. - if comment_match: - comment = comment_match.group(0) - string = string[len(comment):] - elif number_match: - number = number_match.group(0) - yield NumberToken(float(number)) - string = string[len(number):] - elif identifier_match: - identifier = identifier_match.group(0) - # Check if we matched a keyword. - if identifier == 'def': - yield DefToken() - elif identifier == 'extern': - yield ExternToken() - elif identifier == 'if': - yield IfToken() - elif identifier == 'then': - yield ThenToken() - elif identifier == 'else': - yield ElseToken() - elif identifier == 'for': - yield ForToken() - elif identifier == 'in': - yield InToken() - elif identifier == 'binary': - yield BinaryToken() - elif identifier == 'unary': - yield UnaryToken() - elif identifier == 'var': - yield VarToken() - else: - yield IdentifierToken(identifier) - string = string[len(identifier):] - else: - # Yield the ASCII value of the unknown character. - yield CharacterToken(string[0]) - string = string[1:] - - yield EOFToken() - - Abstract Syntax Tree (aka Parse Tree) - ------------------------------------- +Abstract Syntax Tree (aka Parse Tree) +------------------------------------- + +.. code-block:: python # Base class for all expression nodes. - class ExpressionNode(object): pass + class ExpressionNode(object): + pass # Expression class for numeric literals like "1.0". class NumberExpressionNode(ExpressionNode): - def __init__(self, value): self.value = value - - def CodeGen(self): return Constant.real(Type.double(), self.value) + def __init__(self, value): + self.value = value + + def CodeGen(self): + return Constant.real(Type.double(), self.value) # Expression class for referencing a variable, like "a". class VariableExpressionNode(ExpressionNode): - def __init__(self, name): self.name = name - - def CodeGen(self): if self.name in g_named_values: return - g_llvm_builder.load(g_named_values[self.name], self.name) else: - raise RuntimeError('Unknown variable name: ' + self.name) + def __init__(self, name): + self.name = name + + def CodeGen(self): + if self.name in g_named_values: + return g_llvm_builder.load(g_named_values[self.name], self.name) + else: + raise RuntimeError('Unknown variable name: ' + self.name) # Expression class for a binary operator. class BinaryOperatorExpressionNode(ExpressionNode): - def __init__(self, operator, left, right): self.operator = operator - self.left = left self.right = right - - def CodeGen(self): # A special case for '=' because we don't want to - emit the LHS as an # expression. if self.operator == '=': # Assignment - requires the LHS to be an identifier. if not isinstance(self.left, - VariableExpressionNode): raise RuntimeError('Destination of "=" must be - a variable.') - - :: - - # Codegen the RHS. - value = self.right.CodeGen() - - # Look up the name. - variable = g_named_values[self.left.name] - - # Store the value and return it. - g_llvm_builder.store(value, variable) - - return value - - left = self.left.CodeGen() - right = self.right.CodeGen() - - if self.operator == '+': - return g_llvm_builder.fadd(left, right, 'addtmp') - elif self.operator == '-': - return g_llvm_builder.fsub(left, right, 'subtmp') - elif self.operator == '*': - return g_llvm_builder.fmul(left, right, 'multmp') - elif self.operator == '<': - result = g_llvm_builder.fcmp(FCMP_ULT, left, right, 'cmptmp') - # Convert bool 0 or 1 to double 0.0 or 1.0. - return g_llvm_builder.uitofp(result, Type.double(), 'booltmp') - else: - function = g_llvm_module.get_function_named('binary' + self.operator) - return g_llvm_builder.call(function, [left, right], 'binop') + def __init__(self, operator, left, right): + self.operator = operator + self.left = left + self.right = right + + def CodeGen(self): + # A special case for '=' because we don't want to emit the LHS as an # expression. + if self.operator == '=': + # Assignment requires the LHS to be an identifier. + if not isinstance(self.left, VariableExpressionNode): + raise RuntimeError('Destination of "=" must be a variable.') + + # Codegen the RHS. + value = self.right.CodeGen() + + # Look up the name. + variable = g_named_values[self.left.name] + + # Store the value and return it. + g_llvm_builder.store(value, variable) + + return value + + left = self.left.CodeGen() + right = self.right.CodeGen() + + if self.operator == '+': + return g_llvm_builder.fadd(left, right, 'addtmp') + elif self.operator == '-': + return g_llvm_builder.fsub(left, right, 'subtmp') + elif self.operator == '*': + return g_llvm_builder.fmul(left, right, 'multmp') + elif self.operator == '<': + result = g_llvm_builder.fcmp(FCMP_ULT, left, right, 'cmptmp') + # Convert bool 0 or 1 to double 0.0 or 1.0. + return g_llvm_builder.uitofp(result, Type.double(), 'booltmp') + else: + function = g_llvm_module.get_function_named('binary' + self.operator) + return g_llvm_builder.call(function, [left, right], 'binop') # Expression class for function calls. class CallExpressionNode(ExpressionNode): - def __init__(self, callee, args): self.callee = callee self.args = - args - - def CodeGen(self): # Look up the name in the global module table. callee - = g_llvm_module.get_function_named(self.callee) - - :: - - # Check for argument mismatch error. - if len(callee.args) != len(self.args): - raise RuntimeError('Incorrect number of arguments passed.') - - arg_values = [i.CodeGen() for i in self.args] - - return g_llvm_builder.call(callee, arg_values, 'calltmp') + def __init__(self, callee, args): + self.callee = callee + self.args = args + + def CodeGen(self): + # Look up the name in the global module table. + callee = g_llvm_module.get_function_named(self.callee) + + # Check for argument mismatch error. + if len(callee.args) != len(self.args): + raise RuntimeError('Incorrect number of arguments passed.') + + arg_values = [i.CodeGen() for i in self.args] + + return g_llvm_builder.call(callee, arg_values, 'calltmp') # Expression class for if/then/else. class IfExpressionNode(ExpressionNode): - def __init__(self, condition, then_branch, else_branch): - self.condition = condition self.then_branch = then_branch - self.else_branch = else_branch - - def CodeGen(self): condition = self.condition.CodeGen() - - :: - - # Convert condition to a bool by comparing equal to 0.0. - condition_bool = g_llvm_builder.fcmp( - FCMP_ONE, condition, Constant.real(Type.double(), 0), 'ifcond') - - function = g_llvm_builder.basic_block.function - - # Create blocks for the then and else cases. Insert the 'then' block at the - # end of the function. - then_block = function.append_basic_block('then') - else_block = function.append_basic_block('else') - merge_block = function.append_basic_block('ifcond') - - g_llvm_builder.cbranch(condition_bool, then_block, else_block) - - # Emit then value. - g_llvm_builder.position_at_end(then_block) - then_value = self.then_branch.CodeGen() - g_llvm_builder.branch(merge_block) - - # Codegen of 'Then' can change the current block; update then_block for the - # PHI node. - then_block = g_llvm_builder.basic_block - - # Emit else block. - g_llvm_builder.position_at_end(else_block) - else_value = self.else_branch.CodeGen() - g_llvm_builder.branch(merge_block) - - # Codegen of 'Else' can change the current block, update else_block for the - # PHI node. - else_block = g_llvm_builder.basic_block - - # Emit merge block. - g_llvm_builder.position_at_end(merge_block) - phi = g_llvm_builder.phi(Type.double(), 'iftmp') - phi.add_incoming(then_value, then_block) - phi.add_incoming(else_value, else_block) - - return phi + def __init__(self, condition, then_branch, else_branch): + self.condition = condition + self.then_branch = then_branch + self.else_branch = else_branch + + def CodeGen(self): + condition = self.condition.CodeGen() + + # Convert condition to a bool by comparing equal to 0.0. + condition_bool = g_llvm_builder.fcmp( + FCMP_ONE, condition, Constant.real(Type.double(), 0), 'ifcond') + + function = g_llvm_builder.basic_block.function + + # Create blocks for the then and else cases. Insert the 'then' block at the + # end of the function. + then_block = function.append_basic_block('then') + else_block = function.append_basic_block('else') + merge_block = function.append_basic_block('ifcond') + + g_llvm_builder.cbranch(condition_bool, then_block, else_block) + + # Emit then value. + g_llvm_builder.position_at_end(then_block) + then_value = self.then_branch.CodeGen() + g_llvm_builder.branch(merge_block) + + # Codegen of 'Then' can change the current block; update then_block for the + # PHI node. + then_block = g_llvm_builder.basic_block + + # Emit else block. + g_llvm_builder.position_at_end(else_block) + else_value = self.else_branch.CodeGen() + g_llvm_builder.branch(merge_block) + + # Codegen of 'Else' can change the current block, update else_block for the + # PHI node. + else_block = g_llvm_builder.basic_block + + # Emit merge block. + g_llvm_builder.position_at_end(merge_block) + phi = g_llvm_builder.phi(Type.double(), 'iftmp') + phi.add_incoming(then_value, then_block) + phi.add_incoming(else_value, else_block) + + return phi # Expression class for for/in. class ForExpressionNode(ExpressionNode): - def __init__(self, loop_variable, start, end, step, body): - self.loop_variable = loop_variable self.start = start self.end = end - self.step = step self.body = body - - def CodeGen(self): # Output this as: # var = alloca double # ... # start - = startexpr # store start -> var # goto loop # loop: # ... # bodyexpr # - ... # loopend: # step = stepexpr # endcond = endexpr # # curvar = load - var # nextvar = curvar + step # store nextvar -> var # br endcond, loop, - endloop # outloop: - - :: - - function = g_llvm_builder.basic_block.function - - # Create an alloca for the variable in the entry block. - alloca = CreateEntryBlockAlloca(function, self.loop_variable) - - # Emit the start code first, without 'variable' in scope. - start_value = self.start.CodeGen() - - # Store the value into the alloca. - g_llvm_builder.store(start_value, alloca) - - # Make the new basic block for the loop, inserting after current block. - loop_block = function.append_basic_block('loop') - - # Insert an explicit fall through from the current block to the loop_block. - g_llvm_builder.branch(loop_block) - - # Start insertion in loop_block. - g_llvm_builder.position_at_end(loop_block) - - # Within the loop, the variable is defined equal to the alloca. If it - # shadows an existing variable, we have to restore it, so save it now. - old_value = g_named_values.get(self.loop_variable, None) - g_named_values[self.loop_variable] = alloca - - # Emit the body of the loop. This, like any other expr, can change the - # current BB. Note that we ignore the value computed by the body. - self.body.CodeGen() - - # Emit the step value. - if self.step: - step_value = self.step.CodeGen() - else: - # If not specified, use 1.0. - step_value = Constant.real(Type.double(), 1) - - # Compute the end condition. - end_condition = self.end.CodeGen() - - # Reload, increment, and restore the alloca. This handles the case where - # the body of the loop mutates the variable. - cur_value = g_llvm_builder.load(alloca, self.loop_variable) - next_value = g_llvm_builder.fadd(cur_value, step_value, 'nextvar') - g_llvm_builder.store(next_value, alloca) - - # Convert condition to a bool by comparing equal to 0.0. - end_condition_bool = g_llvm_builder.fcmp( - FCMP_ONE, end_condition, Constant.real(Type.double(), 0), 'loopcond') - - # Create the "after loop" block and insert it. - after_block = function.append_basic_block('afterloop') - - # Insert the conditional branch into the end of loop_block. - g_llvm_builder.cbranch(end_condition_bool, loop_block, after_block) - - # Any new code will be inserted in after_block. - g_llvm_builder.position_at_end(after_block) - - # Restore the unshadowed variable. - if old_value is not None: - g_named_values[self.loop_variable] = old_value - else: - del g_named_values[self.loop_variable] - - # for expr always returns 0.0. - return Constant.real(Type.double(), 0) + def __init__(self, loop_variable, start, end, step, body): + self.loop_variable = loop_variable + self.start = start + self.end = end + self.step = step + self.body = body + + def CodeGen(self): + # Output this as: + # var = alloca double + # ... + # start = startexpr + # store start -> var + # goto loop + # loop: + # ... + # bodyexpr + # ... + # loopend: + # step = stepexpr + # endcond = endexpr + # + # curvar = load var + # nextvar = curvar + step + # store nextvar -> var + # br endcond, loop, endloop + # outloop: + + function = g_llvm_builder.basic_block.function + + # Create an alloca for the variable in the entry block. + alloca = CreateEntryBlockAlloca(function, self.loop_variable) + + # Emit the start code first, without 'variable' in scope. + start_value = self.start.CodeGen() + + # Store the value into the alloca. + g_llvm_builder.store(start_value, alloca) + + # Make the new basic block for the loop, inserting after current block. + loop_block = function.append_basic_block('loop') + + # Insert an explicit fall through from the current block to the loop_block. + g_llvm_builder.branch(loop_block) + + # Start insertion in loop_block. + g_llvm_builder.position_at_end(loop_block) + + # Within the loop, the variable is defined equal to the alloca. If it + # shadows an existing variable, we have to restore it, so save it now. + old_value = g_named_values.get(self.loop_variable, None) + g_named_values[self.loop_variable] = alloca + + # Emit the body of the loop. This, like any other expr, can change the + # current BB. Note that we ignore the value computed by the body. + self.body.CodeGen() + + # Emit the step value. + if self.step: + step_value = self.step.CodeGen() + else: + # If not specified, use 1.0. + step_value = Constant.real(Type.double(), 1) + + # Compute the end condition. + end_condition = self.end.CodeGen() + + # Reload, increment, and restore the alloca. This handles the case where + # the body of the loop mutates the variable. + cur_value = g_llvm_builder.load(alloca, self.loop_variable) + next_value = g_llvm_builder.fadd(cur_value, step_value, 'nextvar') + g_llvm_builder.store(next_value, alloca) + + # Convert condition to a bool by comparing equal to 0.0. + end_condition_bool = g_llvm_builder.fcmp( + FCMP_ONE, end_condition, Constant.real(Type.double(), 0), 'loopcond') + + # Create the "after loop" block and insert it. + after_block = function.append_basic_block('afterloop') + + # Insert the conditional branch into the end of loop_block. + g_llvm_builder.cbranch(end_condition_bool, loop_block, after_block) + + # Any new code will be inserted in after_block. + g_llvm_builder.position_at_end(after_block) + + # Restore the unshadowed variable. + if old_value is not None: + g_named_values[self.loop_variable] = old_value + else: + del g_named_values[self.loop_variable] + + # for expr always returns 0.0. + return Constant.real(Type.double(), 0) # Expression class for a unary operator. class UnaryExpressionNode(ExpressionNode): - def __init__(self, operator, operand): self.operator = operator - self.operand = operand - - def CodeGen(self): operand = self.operand.CodeGen() function = - g_llvm_module.get_function_named('unary' + self.operator) return - g_llvm_builder.call(function, [operand], 'unop') + def __init__(self, operator, operand): + self.operator = operator + self.operand = operand + + def CodeGen(self): + operand = self.operand.CodeGen() + function = g_llvm_module.get_function_named('unary' + self.operator) + return g_llvm_builder.call(function, [operand], 'unop') # Expression class for var/in. class VarExpressionNode(ExpressionNode): - def __init__(self, variables, body): self.variables = variables - self.body = body - - def CodeGen(self): old_bindings = {} function = - g_llvm_builder.basic_block.function - - :: - - # Register all variables and emit their initializer. - for var_name, var_expression in self.variables.iteritems(): - # Emit the initializer before adding the variable to scope, this prevents - # the initializer from referencing the variable itself, and permits stuff - # like this: - # var a = 1 in - # var a = a in ... # refers to outer 'a'. - if var_expression is not None: - var_value = var_expression.CodeGen() - else: - var_value = Constant.real(Type.double(), 0) - - alloca = CreateEntryBlockAlloca(function, var_name) - g_llvm_builder.store(var_value, alloca) - - # Remember the old variable binding so that we can restore the binding - # when we unrecurse. - old_bindings[var_name] = g_named_values.get(var_name, None) - - # Remember this binding. - g_named_values[var_name] = alloca - - # Codegen the body, now that all vars are in scope. - body = self.body.CodeGen() - - # Pop all our variables from scope. - for var_name in self.variables: - if old_bindings[var_name] is not None: - g_named_values[var_name] = old_bindings[var_name] - else: - del g_named_values[var_name] - - # Return the body computation. - return body + def __init__(self, variables, body): + self.variables = variables + self.body = body + + def CodeGen(self): + old_bindings = {} + function = g_llvm_builder.basic_block.function + + # Register all variables and emit their initializer. + for var_name, var_expression in self.variables.iteritems(): + # Emit the initializer before adding the variable to scope, this prevents + # the initializer from referencing the variable itself, and permits stuff + # like this: + # var a = 1 in + # var a = a in ... # refers to outer 'a'. + if var_expression is not None: + var_value = var_expression.CodeGen() + else: + var_value = Constant.real(Type.double(), 0) + + alloca = CreateEntryBlockAlloca(function, var_name) + g_llvm_builder.store(var_value, alloca) + + # Remember the old variable binding so that we can restore the binding + # when we unrecurse. + old_bindings[var_name] = g_named_values.get(var_name, None) + + # Remember this binding. + g_named_values[var_name] = alloca + + # Codegen the body, now that all vars are in scope. + body = self.body.CodeGen() + + # Pop all our variables from scope. + for var_name in self.variables: + if old_bindings[var_name] is not None: + g_named_values[var_name] = old_bindings[var_name] + else: + del g_named_values[var_name] + + # Return the body computation. + return body # This class represents the "prototype" for a function, which captures its name, # and its argument names (thus implicitly the number of arguments the function # takes), as well as if it is an operator. class PrototypeNode(object): - def __init__(self, name, args, is_operator=False, precedence=0): - self.name = name self.args = args self.is_operator = is_operator - self.precedence = precedence - - def IsBinaryOp(self): return self.is_operator and len(self.args) == 2 - - def GetOperatorName(self): assert self.is_operator return self.name[-1] - - def CodeGen(self): # Make the function type, eg. double(double,double). - funct_type = Type.function( Type.double(), [Type.double()] * - len(self.args), False) - - :: - - function = Function.new(g_llvm_module, funct_type, self.name) - - # If the name conflicted, there was already something with the same name. - # If it has a body, don't allow redefinition or reextern. - if function.name != self.name: - function.delete() - function = g_llvm_module.get_function_named(self.name) - - # If the function already has a body, reject this. - if not function.is_declaration: - raise RuntimeError('Redefinition of function.') - - # If the function took a different number of args, reject. - if len(function.args) != len(self.args): - raise RuntimeError('Redeclaration of a function with different number ' - 'of args.') - - # Set names for all arguments and add them to the variables symbol table. - for arg, arg_name in zip(function.args, self.args): - arg.name = arg_name - - return function - - # Create an alloca for each argument and register the argument in the - symbol # table so that references to it will succeed. def - CreateArgumentAllocas(self, function): for arg_name, arg in - zip(self.args, function.args): alloca = CreateEntryBlockAlloca(function, - arg_name) g_llvm_builder.store(arg, alloca) - g_named_values[arg_name] = alloca + def __init__(self, name, args, is_operator=False, precedence=0): + self.name = name + self.args = args + self.is_operator = is_operator + self.precedence = precedence + + def IsBinaryOp(self): + return self.is_operator and len(self.args) == 2 + + def GetOperatorName(self): + assert self.is_operator + return self.name[-1] + + def CodeGen(self): + # Make the function type, eg. double(double,double). + funct_type = Type.function( + Type.double(), [Type.double()] * len(self.args), False) + + function = Function.new(g_llvm_module, funct_type, self.name) + + # If the name conflicted, there was already something with the same name. + # If it has a body, don't allow redefinition or reextern. + if function.name != self.name: + function.delete() + function = g_llvm_module.get_function_named(self.name) + + # If the function already has a body, reject this. + if not function.is_declaration: + raise RuntimeError('Redefinition of function.') + + # If the function took a different number of args, reject. + if len(function.args) != len(self.args): + raise RuntimeError('Redeclaration of a function with different number ' + 'of args.') + + # Set names for all arguments and add them to the variables symbol table. + for arg, arg_name in zip(function.args, self.args): + arg.name = arg_name + + return function + + # Create an alloca for each argument and register the argument in the symbol + # table so that references to it will succeed. + def CreateArgumentAllocas(self, function): + for arg_name, arg in zip(self.args, function.args): + alloca = CreateEntryBlockAlloca(function, arg_name) + g_llvm_builder.store(arg, alloca) + g_named_values[arg_name] = alloca # This class represents a function definition itself. class FunctionNode(object): - def __init__(self, prototype, body): self.prototype = prototype - self.body = body + def __init__(self, prototype, body): + self.prototype = prototype + self.body = body + + def CodeGen(self): + # Clear scope. + g_named_values.clear() + + # Create a function object. + function = self.prototype.CodeGen() + + # If this is a binary operator, install its precedence. + if self.prototype.IsBinaryOp(): + operator = self.prototype.GetOperatorName() + g_binop_precedence[operator] = self.prototype.precedence + + # Create a new basic block to start insertion into. + block = function.append_basic_block('entry') + global g_llvm_builder + g_llvm_builder = Builder.new(block) + + # Add all arguments to the symbol table and create their allocas. + self.prototype.CreateArgumentAllocas(function) + + # Finish off the function. + try: + return_value = self.body.CodeGen() + g_llvm_builder.ret(return_value) + + # Validate the generated code, checking for consistency. + function.verify() + + # Optimize the function. + g_llvm_pass_manager.run(function) + except: + function.delete() + if self.prototype.IsBinaryOp(): + del g_binop_precedence[self.prototype.GetOperatorName()] + raise + + return function - def CodeGen(self): # Clear scope. g_named_values.clear() - - :: - - # Create a function object. - function = self.prototype.CodeGen() - - # If this is a binary operator, install its precedence. - if self.prototype.IsBinaryOp(): - operator = self.prototype.GetOperatorName() - g_binop_precedence[operator] = self.prototype.precedence - - # Create a new basic block to start insertion into. - block = function.append_basic_block('entry') - global g_llvm_builder - g_llvm_builder = Builder.new(block) - - # Add all arguments to the symbol table and create their allocas. - self.prototype.CreateArgumentAllocas(function) - - # Finish off the function. - try: - return_value = self.body.CodeGen() - g_llvm_builder.ret(return_value) - - # Validate the generated code, checking for consistency. - function.verify() - - # Optimize the function. - g_llvm_pass_manager.run(function) - except: - function.delete() - if self.prototype.IsBinaryOp(): - del g_binop_precedence[self.prototype.GetOperatorName()] - raise - - return function - - Parser - ------ +Parser +------ + +.. code-block:: python class Parser(object): - def __init__(self, tokens): self.tokens = tokens self.Next() - - # Provide a simple token buffer. Parser.current is the current token the - # parser is looking at. Parser.Next() reads another token from the lexer - and # updates Parser.current with its results. def Next(self): - self.current = self.tokens.next() - - # Gets the precedence of the current token, or -1 if the token is not a - binary # operator. def GetCurrentTokenPrecedence(self): if - isinstance(self.current, CharacterToken): return - g_binop_precedence.get(self.current.char, -1) else: return -1 - - # identifierexpr ::= identifier | identifier '(' expression* ')' def - ParseIdentifierExpr(self): identifier_name = self.current.name - self.Next() # eat identifier. - - :: - - if self.current != CharacterToken('('): # Simple variable reference. - return VariableExpressionNode(identifier_name) - - # Call. - self.Next() # eat '('. - args = [] - if self.current != CharacterToken(')'): - while True: - args.append(self.ParseExpression()) - if self.current == CharacterToken(')'): - break - elif self.current != CharacterToken(','): - raise RuntimeError('Expected ")" or "," in argument list.') - self.Next() - - self.Next() # eat ')'. - return CallExpressionNode(identifier_name, args) - - # numberexpr ::= number def ParseNumberExpr(self): result = - NumberExpressionNode(self.current.value) self.Next() # consume the - number. return result - - # parenexpr ::= '(' expression ')' def ParseParenExpr(self): self.Next() - # eat '('. - - :: - - contents = self.ParseExpression() - - if self.current != CharacterToken(')'): - raise RuntimeError('Expected ")".') - self.Next() # eat ')'. - - return contents - - # ifexpr ::= 'if' expression 'then' expression 'else' expression def - ParseIfExpr(self): self.Next() # eat the if. - - :: - - # condition. - condition = self.ParseExpression() - - if not isinstance(self.current, ThenToken): - raise RuntimeError('Expected "then".') - self.Next() # eat the then. - - then_branch = self.ParseExpression() - - if not isinstance(self.current, ElseToken): - raise RuntimeError('Expected "else".') - self.Next() # eat the else. - - else_branch = self.ParseExpression() - - return IfExpressionNode(condition, then_branch, else_branch) - - # forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' - expression def ParseForExpr(self): self.Next() # eat the for. - - :: - - if not isinstance(self.current, IdentifierToken): - raise RuntimeError('Expected identifier after for.') - - loop_variable = self.current.name - self.Next() # eat the identifier. - - if self.current != CharacterToken('='): - raise RuntimeError('Expected "=" after for variable.') - self.Next() # eat the '='. - - start = self.ParseExpression() - - if self.current != CharacterToken(','): - raise RuntimeError('Expected "," after for start value.') - self.Next() # eat the ','. - - end = self.ParseExpression() - - # The step value is optional. - if self.current == CharacterToken(','): - self.Next() # eat the ','. - step = self.ParseExpression() - else: - step = None - - if not isinstance(self.current, InToken): - raise RuntimeError('Expected "in" after for variable specification.') - self.Next() # eat 'in'. - - body = self.ParseExpression() - - return ForExpressionNode(loop_variable, start, end, step, body) - - # varexpr ::= 'var' (identifier ('=' expression)?)+ 'in' expression def - ParseVarExpr(self): self.Next() # eat 'var'. - - :: - - variables = {} - - # At least one variable name is required. - if not isinstance(self.current, IdentifierToken): - raise RuntimeError('Expected identifier after "var".') - - while True: - var_name = self.current.name - self.Next() # eat the identifier. - - # Read the optional initializer. - if self.current == CharacterToken('='): - self.Next() # eat '='. - variables[var_name] = self.ParseExpression() - else: - variables[var_name] = None - - # End of var list, exit loop. - if self.current != CharacterToken(','): - break - self.Next() # eat ','. - - if not isinstance(self.current, IdentifierToken): - raise RuntimeError('Expected identifier after "," in a var expression.') - - # At this point, we have to have 'in'. - if not isinstance(self.current, InToken): - raise RuntimeError('Expected "in" keyword after "var".') - self.Next() # eat 'in'. - - body = self.ParseExpression() - - return VarExpressionNode(variables, body) - - # primary ::= # dentifierexpr | numberexpr | parenexpr | ifexpr | - forexpr | varexpr def ParsePrimary(self): if isinstance(self.current, - IdentifierToken): return self.ParseIdentifierExpr() elif - isinstance(self.current, NumberToken): return self.ParseNumberExpr() - elif isinstance(self.current, IfToken): return self.ParseIfExpr() elif - isinstance(self.current, ForToken): return self.ParseForExpr() elif - isinstance(self.current, VarToken): return self.ParseVarExpr() elif - self.current == CharacterToken('('): return self.ParseParenExpr() else: - raise RuntimeError('Unknown token when expecting an expression.') - - # unary ::= primary | unary_operator unary def ParseUnary(self): # If - the current token is not an operator, it must be a primary expression. - if (not isinstance(self.current, CharacterToken) or self.current in - [CharacterToken('('), CharacterToken(',')]): return self.ParsePrimary() - - :: - - # If this is a unary operator, read it. - operator = self.current.char - self.Next() # eat the operator. - return UnaryExpressionNode(operator, self.ParseUnary()) - - # binoprhs ::= (binary_operator unary)* def ParseBinOpRHS(self, left, - left_precedence): # If this is a binary operator, find its precedence. - while True: precedence = self.GetCurrentTokenPrecedence() - - :: - - # If this is a binary operator that binds at least as tightly as the - # current one, consume it; otherwise we are done. - if precedence < left_precedence: - return left - - binary_operator = self.current.char - self.Next() # eat the operator. - - # Parse the unary expression after the binary operator. - right = self.ParseUnary() - - # If binary_operator binds less tightly with right than the operator after - # right, let the pending operator take right as its left. - next_precedence = self.GetCurrentTokenPrecedence() - if precedence < next_precedence: - right = self.ParseBinOpRHS(right, precedence + 1) - - # Merge left/right. - left = BinaryOperatorExpressionNode(binary_operator, left, right) - - # expression ::= unary binoprhs def ParseExpression(self): left = - self.ParseUnary() return self.ParseBinOpRHS(left, 0) - - # prototype # ::= id '(' id* ')' # ::= binary LETTER number? (id, id) # - ::= unary LETTER (id) def ParsePrototype(self): precedence = None if - isinstance(self.current, IdentifierToken): kind = 'normal' - function_name = self.current.name self.Next() # eat function name. elif - isinstance(self.current, UnaryToken): kind = 'unary' self.Next() # eat - 'unary'. if not isinstance(self.current, CharacterToken): raise - RuntimeError('Expected an operator after "unary".') function_name = - 'unary' + self.current.char self.Next() # eat the operator. elif - isinstance(self.current, BinaryToken): kind = 'binary' self.Next() # eat - 'binary'. if not isinstance(self.current, CharacterToken): raise - RuntimeError('Expected an operator after "binary".') function_name = - 'binary' + self.current.char self.Next() # eat the operator. if - isinstance(self.current, NumberToken): if not 1 <= self.current.value <= - 100: raise RuntimeError('Invalid precedence: must be in range [1, - 100].') precedence = self.current.value self.Next() # eat the - precedence. else: raise RuntimeError('Expected function name, "unary" or - "binary" in ' 'prototype.') - - :: - - if self.current != CharacterToken('('): - raise RuntimeError('Expected "(" in prototype.') - self.Next() # eat '('. - - arg_names = [] - while isinstance(self.current, IdentifierToken): - arg_names.append(self.current.name) - self.Next() - - if self.current != CharacterToken(')'): - raise RuntimeError('Expected ")" in prototype.') - - # Success. - self.Next() # eat ')'. - - if kind == 'unary' and len(arg_names) != 1: - raise RuntimeError('Invalid number of arguments for a unary operator.') - elif kind == 'binary' and len(arg_names) != 2: - raise RuntimeError('Invalid number of arguments for a binary operator.') - - return PrototypeNode(function_name, arg_names, kind != 'normal', precedence) - - # definition ::= 'def' prototype expression def ParseDefinition(self): - self.Next() # eat def. proto = self.ParsePrototype() body = - self.ParseExpression() return FunctionNode(proto, body) - - # toplevelexpr ::= expression def ParseTopLevelExpr(self): proto = - PrototypeNode('', []) return FunctionNode(proto, self.ParseExpression()) - - # external ::= 'extern' prototype def ParseExtern(self): self.Next() # - eat extern. return self.ParsePrototype() - - # Top-Level parsing def HandleDefinition(self): - self.Handle(self.ParseDefinition, 'Read a function definition:') - - def HandleExtern(self): self.Handle(self.ParseExtern, 'Read an extern:') - - def HandleTopLevelExpression(self): try: function = - self.ParseTopLevelExpr().CodeGen() result = - g_llvm_executor.run_function(function, []) print 'Evaluated to:', - result.as_real(Type.double()) except Exception, e: raise#print - 'Error:', e try: self.Next() # Skip for error recovery. except: pass - - def Handle(self, function, message): try: print message, - function().CodeGen() except Exception, e: raise#print 'Error:', e try: - self.Next() # Skip for error recovery. except: pass - - Main driver code. - ----------------- - - def main(): # Set up the optimizer pipeline. Start with registering info - about how the # target lays out data structures. - g_llvm_pass_manager.add(g_llvm_executor.target_data) # Promote - allocas to registers. - g_llvm_pass_manager.add(PASS_PROMOTE_MEMORY_TO_REGISTER) # Do - simple "peephole" optimizations and bit-twiddling optzns. - g_llvm_pass_manager.add(PASS_INSTRUCTION_COMBINING) # Reassociate - expressions. g_llvm_pass_manager.add(PASS_REASSOCIATE) # Eliminate - Common SubExpressions. g_llvm_pass_manager.add(PASS_GVN) # Simplify - the control flow graph (deleting unreachable blocks, etc). - g_llvm_pass_manager.add(PASS_CFG_SIMPLIFICATION) - - g_llvm_pass_manager.initialize() - - # Install standard binary operators. # 1 is lowest possible precedence. - 40 is the highest. g_binop_precedence['='] = 2 - g_binop_precedence['<'] = 10 g_binop_precedence['+'] = 20 - g_binop_precedence['-'] = 20 g_binop_precedence['*'] = 40 - - # Run the main "interpreter loop". while True: print 'ready<', try: raw - = raw_input() except KeyboardInterrupt: break - - :: - - parser = Parser(Tokenize(raw)) - while True: - # top ::= definition | external | expression | EOF - if isinstance(parser.current, EOFToken): - break - if isinstance(parser.current, DefToken): - parser.HandleDefinition() - elif isinstance(parser.current, ExternToken): - parser.HandleExtern() - else: - parser.HandleTopLevelExpression() - - # Print out all of the generated code. print '', g_llvm_module - - if **name** == '__main__': main() + def __init__(self, tokens): + self.tokens = tokens + self.Next() + + # Provide a simple token buffer. Parser.current is the current token the + # parser is looking at. Parser.Next() reads another token from the lexer and + # updates Parser.current with its results. + def Next(self): + self.current = self.tokens.next() + + # Gets the precedence of the current token, or -1 if the token is not a binary + # operator. + def GetCurrentTokenPrecedence(self): + if isinstance(self.current, CharacterToken): + return g_binop_precedence.get(self.current.char, -1) + else: + return -1 + + # identifierexpr ::= identifier | identifier '(' expression* ')' + def ParseIdentifierExpr(self): + identifier_name = self.current.name + self.Next() # eat identifier. + + if self.current != CharacterToken('('): # Simple variable reference. + return VariableExpressionNode(identifier_name) + + # Call. + self.Next() # eat '('. + args = [] + if self.current != CharacterToken(')'): + while True: + args.append(self.ParseExpression()) + if self.current == CharacterToken(')'): + break + elif self.current != CharacterToken(','): + raise RuntimeError('Expected ")" or "," in argument list.') + self.Next() + + self.Next() # eat ')'. + return CallExpressionNode(identifier_name, args) + + # numberexpr ::= number + def ParseNumberExpr(self): + result = NumberExpressionNode(self.current.value) + self.Next() # consume the number. + return result + + # parenexpr ::= '(' expression ')' + def ParseParenExpr(self): + self.Next() # eat '('. + + contents = self.ParseExpression() + + if self.current != CharacterToken(')'): + raise RuntimeError('Expected ")".') + self.Next() # eat ')'. + + return contents + + # ifexpr ::= 'if' expression 'then' expression 'else' expression + def ParseIfExpr(self): + self.Next() # eat the if. + + # condition. + condition = self.ParseExpression() + + if not isinstance(self.current, ThenToken): + raise RuntimeError('Expected "then".') + self.Next() # eat the then. + + then_branch = self.ParseExpression() + + if not isinstance(self.current, ElseToken): + raise RuntimeError('Expected "else".') + self.Next() # eat the else. + + else_branch = self.ParseExpression() + + return IfExpressionNode(condition, then_branch, else_branch) + + # forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression + def ParseForExpr(self): + self.Next() # eat the for. + + if not isinstance(self.current, IdentifierToken): + raise RuntimeError('Expected identifier after for.') + + loop_variable = self.current.name + self.Next() # eat the identifier. + + if self.current != CharacterToken('='): + raise RuntimeError('Expected "=" after for variable.') + self.Next() # eat the '='. + + start = self.ParseExpression() + + if self.current != CharacterToken(','): + raise RuntimeError('Expected "," after for start value.') + self.Next() # eat the ','. + + end = self.ParseExpression() + + # The step value is optional. + if self.current == CharacterToken(','): + self.Next() # eat the ','. + step = self.ParseExpression() + else: + step = None + + if not isinstance(self.current, InToken): + raise RuntimeError('Expected "in" after for variable specification.') + self.Next() # eat 'in'. + + body = self.ParseExpression() + + return ForExpressionNode(loop_variable, start, end, step, body) + + # varexpr ::= 'var' (identifier ('=' expression)?)+ 'in' expression + def ParseVarExpr(self): + self.Next() # eat 'var'. + + variables = {} + + # At least one variable name is required. + if not isinstance(self.current, IdentifierToken): + raise RuntimeError('Expected identifier after "var".') + + while True: + var_name = self.current.name + self.Next() # eat the identifier. + + # Read the optional initializer. + if self.current == CharacterToken('='): + self.Next() # eat '='. + variables[var_name] = self.ParseExpression() + else: + variables[var_name] = None + + # End of var list, exit loop. + if self.current != CharacterToken(','): + break + self.Next() # eat ','. + + if not isinstance(self.current, IdentifierToken): + raise RuntimeError('Expected identifier after "," in a var expression.') + + # At this point, we have to have 'in'. + if not isinstance(self.current, InToken): + raise RuntimeError('Expected "in" keyword after "var".') + self.Next() # eat 'in'. + + body = self.ParseExpression() + + return VarExpressionNode(variables, body) + + # primary ::= + # dentifierexpr | numberexpr | parenexpr | ifexpr | forexpr | varexpr + def ParsePrimary(self): + if isinstance(self.current, IdentifierToken): + return self.ParseIdentifierExpr() + elif isinstance(self.current, NumberToken): + return self.ParseNumberExpr() + elif isinstance(self.current, IfToken): + return self.ParseIfExpr() + elif isinstance(self.current, ForToken): + return self.ParseForExpr() + elif isinstance(self.current, VarToken): + return self.ParseVarExpr() + elif self.current == CharacterToken('('): + return self.ParseParenExpr() + else: + raise RuntimeError('Unknown token when expecting an expression.') + + # unary ::= primary | unary_operator unary + def ParseUnary(self): + # If the current token is not an operator, it must be a primary expression. + if (not isinstance(self.current, CharacterToken) or + self.current in [CharacterToken('('), CharacterToken(',')]): + return self.ParsePrimary() + + # If this is a unary operator, read it. + operator = self.current.char + self.Next() # eat the operator. + return UnaryExpressionNode(operator, self.ParseUnary()) + + # binoprhs ::= (binary_operator unary)* + def ParseBinOpRHS(self, left, left_precedence): + # If this is a binary operator, find its precedence. + while True: + precedence = self.GetCurrentTokenPrecedence() + + # If this is a binary operator that binds at least as tightly as the + # current one, consume it; otherwise we are done. + if precedence < left_precedence: + return left + + binary_operator = self.current.char + self.Next() # eat the operator. + + # Parse the unary expression after the binary operator. + right = self.ParseUnary() + + # If binary_operator binds less tightly with right than the operator after + # right, let the pending operator take right as its left. + next_precedence = self.GetCurrentTokenPrecedence() + if precedence < next_precedence: + right = self.ParseBinOpRHS(right, precedence + 1) + + # Merge left/right. + left = BinaryOperatorExpressionNode(binary_operator, left, right) + + # expression ::= unary binoprhs + def ParseExpression(self): + left = self.ParseUnary() + return self.ParseBinOpRHS(left, 0) + + # prototype + # ::= id '(' id* ')' + # ::= binary LETTER number? (id, id) + # ::= unary LETTER (id) + def ParsePrototype(self): + precedence = None + if isinstance(self.current, IdentifierToken): + kind = 'normal' + function_name = self.current.name + self.Next() # eat function name. + elif isinstance(self.current, UnaryToken): + kind = 'unary' + self.Next() # eat 'unary'. + if not isinstance(self.current, CharacterToken): + raise RuntimeError('Expected an operator after "unary".') + function_name = 'unary' + self.current.char + self.Next() # eat the operator. + elif isinstance(self.current, BinaryToken): + kind = 'binary' + self.Next() # eat 'binary'. + if not isinstance(self.current, CharacterToken): + raise RuntimeError('Expected an operator after "binary".') + function_name = 'binary' + self.current.char + self.Next() # eat the operator. + if isinstance(self.current, NumberToken): + if not 1 <= self.current.value <= 100: + raise RuntimeError('Invalid precedence: must be in range [1, 100].') + precedence = self.current.value + self.Next() # eat the precedence. + else: + raise RuntimeError('Expected function name, "unary" or "binary" in ' + 'prototype.') + + if self.current != CharacterToken('('): + raise RuntimeError('Expected "(" in prototype.') + self.Next() # eat '('. + + arg_names = [] + while isinstance(self.current, IdentifierToken): + arg_names.append(self.current.name) + self.Next() + + if self.current != CharacterToken(')'): + raise RuntimeError('Expected ")" in prototype.') + + # Success. + self.Next() # eat ')'. + + if kind == 'unary' and len(arg_names) != 1: + raise RuntimeError('Invalid number of arguments for a unary operator.') + elif kind == 'binary' and len(arg_names) != 2: + raise RuntimeError('Invalid number of arguments for a binary operator.') + + return PrototypeNode(function_name, arg_names, kind != 'normal', precedence) + + # definition ::= 'def' prototype expression + def ParseDefinition(self): + self.Next() # eat def. + proto = self.ParsePrototype() + body = self.ParseExpression() + return FunctionNode(proto, body) + + # toplevelexpr ::= expression + def ParseTopLevelExpr(self): + proto = PrototypeNode('', []) + return FunctionNode(proto, self.ParseExpression()) + + # external ::= 'extern' prototype + def ParseExtern(self): + self.Next() # eat extern. + return self.ParsePrototype() + + # Top-Level parsing + def HandleDefinition(self): + self.Handle(self.ParseDefinition, 'Read a function definition:') + + def HandleExtern(self): + self.Handle(self.ParseExtern, 'Read an extern:') + + def HandleTopLevelExpression(self): + try: + function = self.ParseTopLevelExpr().CodeGen() + result = g_llvm_executor.run_function(function, []) + print 'Evaluated to:', result.as_real(Type.double()) + except Exception, e: + raise#print 'Error:', e + try: + self.Next() # Skip for error recovery. + except: + pass + + def Handle(self, function, message): + try: + print message, function().CodeGen() + except Exception, e: + raise#print 'Error:', e + try: + self.Next() # Skip for error recovery. + except: + pass + +Main driver code. +----------------- + +.. code-block:: python + + def main(): + # Set up the optimizer pipeline. Start with registering info about how the + # target lays out data structures. + g_llvm_pass_manager.add(g_llvm_executor.target_data) + # Promote allocas to registers. + g_llvm_pass_manager.add(PASS_PROMOTE_MEMORY_TO_REGISTER) + # Do simple "peephole" optimizations and bit-twiddling optzns. + g_llvm_pass_manager.add(PASS_INSTRUCTION_COMBINING) + # Reassociate expressions. + g_llvm_pass_manager.add(PASS_REASSOCIATE) + # Eliminate Common SubExpressions. + g_llvm_pass_manager.add(PASS_GVN) + # Simplify the control flow graph (deleting unreachable blocks, etc). + g_llvm_pass_manager.add(PASS_CFG_SIMPLIFICATION) + + g_llvm_pass_manager.initialize() + + # Install standard binary operators. + # 1 is lowest possible precedence. 40 is the highest. + g_binop_precedence['='] = 2 + g_binop_precedence['<'] = 10 + g_binop_precedence['+'] = 20 + g_binop_precedence['-'] = 20 + g_binop_precedence['*'] = 40 + + # Run the main "interpreter loop". + while True: + print 'ready<', + try: + raw = raw_input() + except KeyboardInterrupt: + break + + parser = Parser(Tokenize(raw)) + while True: + # top ::= definition | external | expression | EOF + if isinstance(parser.current, EOFToken): + break + if isinstance(parser.current, DefToken): + parser.HandleDefinition() + elif isinstance(parser.current, ExternToken): + parser.HandleExtern() + else: + parser.HandleTopLevelExpression() + + # Print out all of the generated code. + print '', g_llvm_module + + if __name__ == '__main__': + main()